387. First Unique Character in a String

387. First Unique Character in a String



public class Solution{
  public int firstUniqChar(String s){
    HashMap<Character, Integer> map = new HashMap<>();
    for(int i = 0; i < s.length(); i++){
      char c = s.charAt(i);
      Integer count = map.get(c);
      if(count == null){
        map.put(c, 1);
      }else{
        map.put(c, count + 1);
      }
    }
    
    for(int i = 0; i < s.length(); i++){
      if(map.get(s.charAt(i)) == 1){
        return i;
      }
    }
    return -1;
  }
}

 

Given a string, find the first non-repeating character in it and return it's index. If it doesn't exist, return -1.

Examples:

s = "leetcode"
return 0.

s = "loveleetcode",
return 2.